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Original question:

TMS320F28335: F28335

TMS320F28335: F28335

Anu B
Intellectual 335 points
Part Number: TMS320F28335


Hello,

I have been going through eCAN manual and the manual says: "It is not possible to achieve a direct digital loopback externally by connecting the CANTX and CANRX pins together (as is possible with SCI/SPI/McBSP modules). An internal loopback is possible in the self-test mode (STM)."

I have three doubts:

1. STM is internal loopback within the same CAN module, where the CAN module generates its own ACK signal, right?

2. When the manual says, external loopback is not possible, what does it mean?

Does it mean this: Communication within the same eCANA module by externally connecting the 2 pins is not possible but communication between the 2 modules present in the board: eCANA and eCANB is possible, though this is also called loopback? Or does it mean something else?

3. Why is the external loopback not possible for CAN?

Thanks,

Anu

  • 0
    TI__Guru* 95315 points

    1. STM is internal loopback within the same CAN module, where the CAN module generates its own ACK signal, right?

    Correct. 

    2. When the manual says, external loopback is not possible, what does it mean? Does it mean this: Communication within the same eCANA module by externally connecting the 2 pins is not possible

    Yes, that is exactly what it means. 

    but communication between the 2 modules present in the board: eCANA and eCANB is possible, though this is also called loopback? Or does it mean something else?

    You cannot directly connect the CAN modules together. You either need transceivers or use a "wired AND" for both CANTX where the o/p of the AND is connected to both CANRX pins. 

    3. Why is the external loopback not possible for CAN?

    I have explained this clearly in my Application report http://www.ti.com/lit/spra876